The present invention relates to temperature-stable semiconductor circuits and, more particularly, to a novel voltage reference source with semiconductor amplifiers, which source is both integratable and temperature- and voltage-insensitive.
Analog-to-digital converters (ADC), such as are used in digital control and signal processing systems, generally utilize a voltage reference source which must be insensitive to changes not only in the supply voltage to the voltage reference source and to the ADC but also to changes in ambient temperature. It is desirable to implement a supply- and temperature-insensitive reference voltage source particularly utilizing MOSFET technology, to facilitate incorporation of a reference voltage source upon the same semiconductor chip as the ADC. Additionally, facilitation of a reference voltage source in MOSFET technology would be useful for combining the reference source and its companion ADC in a single chip with microprocessing circuitry for utilization as an analog-input microcontroller.
It is known that MOSFET circuits are relatively temperature-dependent in operation, in that the threshold voltage of a MOSFET device tends to decrease with increasing temperature, typically at a rate of several millivolts per degree centigrade, and that the carrier mobility is also temperature-dependent with the mobility varying at room temperatures, typically to the negative three-half power of temperature. Thus, a voltage reference source and its associated amplifiers, which are immune to threshold voltage and carrier mobility effects, is highly desirable.